What is Fly Line Backing? (Fly Line Backing Explained + Important Points to Consider)

Starting in fly fishing can be a daunting task. So much to consider and find out. What rod to get, what reel to get with it?

The last thing on your mind is fly line backing.

When you are done purchasing your setup, you usually just grab the first spool of backing or ask the shop assistant to spool some backing for you.

It is important to know a little about fly line backing. You don’t have to be a rocket scientist with the stuff, but a few good pointers and must knows, like what lbs to use and how much is enough? These are important questions.

These small things do matter. In the article below, I will run down what I know about fly backing and how I choose and attach it to my reel and fly line. Using the right knot is essential, and you don’t want the backing breaking when you have a fish on the other end.

What Exactly is Fly Line Backing?

Simply put, fly line backing is a Dacron-based line that extends the fly line by a further 50 to 100 yards. It is attached to the reel spool spine and then to the fly line butt end.

Imagine having a running fish, and you just see that fly line disappearing. Your heart starts to pound unnecessarily as you worry about running out of line. This is why we put backing on our fly fish reels.

For further info on fly lines and how to choose them check out these articles:

man casting fly rod and working with fly line

How is it Made?

Fly line backing is available in two types, Dacron and Gel spun, and they both serve the same purpose.

Extending the fly line, so the angler has more to work with than just 30 yards of fly line. This is very needed when fighting big fish. Trust me!

Dacron – is the universal name used for a PETE-constructed polymer. It is extremely strong and has a very low coefficient friction. Dacron comes in 30lbs to 50lbs and is your standard fly line backing choice.

Gel Spun – is the more modern polymer called HMPE. It is the same material used to construct body armor, sailing, and climbing ropes, and its interlinking molecular construction makes it very strong with a reduced diameter size.

Basically, thinner, and stronger!

This is the first choice for fly anglers that chase species that usually run a mile – Tarpon, GT, sailfish, and bonefish, to name a few.

fly fishing rod with a reel and orange fly line

What to Look for?

The obvious decision to make is the breaking strain of backing and how much I need? Well, to make it easier, 20lbs will cover most of your freshwater applications, and the 30-50lbs range would be for the bigger salt species and adventures.

The reel specs will tell roughly how much backing your spool can take, and the size of the arbor will influence its backing capacity. The older reels don’t have much space compared to the more modern reels.

To give you an idea, the ABEL super series 4/5wt reel holds 80 –100yrds of 20lbs Backing.

How Much Fly Line Backing do I Need on My Reel?

As a rule, I like to put my backing on my reels. I have done this for years and recommend you ask the fly shop to do yours for your first time.

The basic ratios for the backing amount needed to reels weight are as follows.

  • 2-3-4wt- 100 yards 20lbs
  • 4-5-6wt- 100-150 yards 20lbs
  • 7-8-9wt- 180-220 yards 20lbs
  • 9-10-12wt 250-400 yards of 30lbs

Please remember that each reel will specify a rough estimate of its backing capacity. Use this as a guideline.

The amount of tension you place on the backing when it is being spooled is essential, and this will determine how much backing can be spooled and if your fly line will fit comfortably on there as well.

Dacron tends to shrink a little when wet, so make sure you allow for this by how taut the backing is applied to the spool. If too taut and it shrinks when wet, the older spool spines would pop!

One of my pet hates it when too much backing has been squeezed on and the person doing this hasn’t considered the WF line size.

So, when it comes to the end of reeling up the last 2 meters fly line, it scrapes on the reel case.

This can damage your fly line coating and is super annoying!

fly fisherman fishing in river

Important Points to Consider

  • Backing is a must! If you are chasing bigger fish that tend to run.
  • With no backing, your space to fight the fish is limited.
  • Color doesn’t matter, really.
  • The knots used are essential.
  • Make sure the tension is correct when applying the backing.
  • Allow enough room for the fly line to fit comfortably.
  • If you haven’t spooled backing before, get it done by someone.
  • Don’t stress if you haven’t put enough on. There is always a next time.

FAQs about Fly Line Backing

What is the difference between the actual line and backing?

Fly line is the actual tapered line that is attached to your leader and then fly. The fly line transfers the energy generated from the fly rod through to the fly, allowing us to cast and get some distance.

The fly line backing is what attaches to the butt end of the fly line and the fly reel spool. This backing gives us an extra line to work with when fighting a fish.

It isn’t imperative when fishing small streams and creeks, but the backing is a must when chasing big fish.

Suppose you choose not to use backing on your small stream’s setup. One note the fly line will develop a horrible line memory because it has been wound around the spool spine in very tight loops. The backing makes the arbor bigger, allowing for less line memory.

angler fly fishing at sunset

Where does my backing go on my setup?

Fly line backing is attached to the spool spine end and then to the fly line butt end. The average freshwater reels can comfortably take 40-50yrds of backing and the fly line without any issues.

As I mentioned earlier, too much backing hinders the fly line towards the end when you are reeling the line in.

A specific knot is used to attach the backing to the spool.

How do you attach the backing?

Many knots can be used to attach the backing to the reel spool and fly line butt end. The best is to find the knots that work for you and use them.

Practice them until you are confident and learn their breaking strains.

Specific knots work better than others, depending on the diameter of the line you are using.

Some knots work better on polymer products instead of mono-based products. ALWAYS wet your knot before you pull them tight, and friction is a reel thing.

Reel end

A simple overhand nail knot is used with a sliding stop at the end. As mentioned, there are many knots, but this is my favorite one to use. Please remember to place the backing and keep the knot the opposite way to the reel when reeling in. This will ensure the line pulls on itself when being reeled in.

Fly line

Again there are many knots use here. The nail/ needle knot, the improved nail knot, or the Albright knot.

The more modern fly lines have welded loops on both ends of the fly line to ease the attachment to the fly line backing and leader.

My personal choice is to create my own perfection loop with the core of the fly line if there isn’t a welded loop.

Simply strip the plastic coating off the butt end of the fly line and tie a tiny perfection loop. You can attach the backing to this with a loop-to-loop connection or a blood knot.

Albright Knot link – Albright Knot

Nail Knot link – Nail Knot

The Nail knot can also be used to attach the leader to your fly line

Do I really need fly line backing?

Yes, I recommend using backing on all fly reels. As mentioned earlier on the smaller stream rod and reel setups, you never really even use the backing. The role of the backing in these smaller setups is to prevent line memory more than added line length.

On the larger setups, it is essential to have the backing. When that Tarpon takes and heads off like a steam train, 35yards of fly line is nothing! Having 200 extra yards of backing is what you need to successfully leader the Tarpon.

How often should I change my backing?

The changing of backing is an openly debated topic. Many say every season, others, every few seasons, and a few say never.

I think for freshwater uses, every few seasons is just fine. For saltwater purposes, I would inspect it every season’s end and decide. I look for nicks and damaged parts that may have rubbed on some coral or a rock. These are weak spots and will probably snap when under tension again.

Are there any alternatives to fly line backing?

The straight answer is no! That said, I have heard of some anglers using mono as a base which isn’t ideal.

Some anglers use a bass fishing braid, which is very similar to a gel spun backing. There aren’t any issues with this. The only thing is to make sure you don’t over tension the braid on the smaller weight reels.

What is the best color for fly line backing, and does it matter?

Fly line backing comes in many different colors. The color you choose isn’t important really. On the bigger reels that take a few hundred yards of the stuff, I like to have specific colors to indicate the amount of line that is off the reel.

The first 100yards can be orange, and the remaining 100 yards can be white. This just gives me an idea of how far the fish is out.

The know to join the two colors must be a strong one. I like to use a loop-to-loop know with two perfection loops as the knots. I have complete faith in this knot and am happy to fight anything on it.

Check out the Perfection loop knot below:

Final Thoughts

So, there you have it. The backing is essential for fly fishing. There are a range of colors and breaking strengths to choose from.

If you are unsure of anything regarding the choice, spooling, or knots of fly line backing, ask for advice.

Shoot us a question in the comments section, and we will happily answer it for you.

Tight Lines!

Bob Hoffmann

The author of this post is Bob Hoffmann. Bob has spend most of his childhood fishing with his father and now share all his knowledge with other anglers. Feel free to leave a comment below.

Recent Content